Coin operated telephone auditor

ABSTRACT

A low-power, integrated coin acceptor for a payphone containing audit circuitry is described. The integrated coin acceptor connects to the telephone tip, ring and ground lines and connects to a dumb or smart payphone chassis to provide both coin validation and audit functions. The integrated coin acceptor is compatible with the audit software used by the central office, and assures a seamless transition between coin acceptor operation, audit data recording and audit information transmission. Components related to the audit function include a line interface to the tip, ring, and ground lines, a DTMF transceiver, battery backed-up RAM memory, EEPROM memory, real time clock, and battery and control circuits for data retention. During audit interrogation activity, the integrated coin acceptor takes control of the phone line, but contains circuitry that will return dial-tone to the user if an off-hook event occurs. Also disclosed are an interface circuit to aid in initializing the audit functions and for checking the availability of telephone line power, and a cashbox security switch for mounting into an existing hole in the telephone chassis housing.

This is a divisional application of copending U.S. application Ser. No.08/681,844 filed on Jul. 29, 1996.

BACKGROUND OF THE INVENTION

The present invention pertains to an integrated electronic coin acceptorand auditor for a coin operated telephone. The integrated coin acceptorvalidates coins, monitors money collection events at the coin telephoneand transmits information to a central location.

Coin operated telephone stations are interfaced with a central office bytip, ring and ground lines. When the handset is lifted off the hook, thecentral office supplies a very small DC loop current, 23 milliamperes(mA) minimum, which is available to the coin operated telephone for useas a source of power. When the handset is on-hook, the recommendedpractice is for a coin operated telephone to draw virtually no currentfrom the phone line.

The deregulation of the telephone industry forced payphone manufacturersto incorporate a number of cost-saving electronic functions and featuresinto their coin telephones. These new devices are known as "smart"payphones because they incorporate a chassis containing computerizedcircuitry to perform a multiplicity of functions not performed byregular or "dumb" payphone units. One of the functions typicallyincluded is the monitoring, counting and recording of all cashtransactions.

Several approaches have been used to address the demand for additionalpayphone functions and features within the constraints of low poweroperation. In some cases, an internal battery is used to supplyadditional power. Other coin operated telephones have simply notincorporated a full range of advanced functions. Yet other prior artcoin telephones draw several milliamps of current when the handset ison-hook to power various functions, thus violating the recommendedpractice and robbing power from other payphones attached to the system.

The operation and maintenance of coin-operated telephones is expensive.One factor that contributes to this expense is the cost to collect themoney from the coin telephones, which typically differs from telephoneto telephone since it can depend greatly on the telephone's location.Any measures that can be taken to reduce the frequency with which thecollections must be made can contribute significantly to theprofitability of operating coin telephones.

One way to reduce the cost of removing the receipts from a particularcoin telephone is to minimize the collection frequency. However,reducing collection frequency beyond a certain point results in lostreceipts, since the telephone cannot be operated once the collection boxis full. Furthermore, since the rate at which a given telephone becomesfilled with coins can vary significantly from time to time, a timeduration that is adequate between collection visits at one time may betoo long at another time and may result in an unnecessary visit at athird time.

The most desired function offered by the smart payphone units is theirability to accurately count and make available a record of all depositedand collected coinage. The auditors keep track of the amount of moneycollected and send the collection information to a central locationwhich utilizes the information to schedule collections. Some systemsinclude equipment and software at the central location to poll theremote auditors at predetermined time intervals. In other systems, eachcoin telephone auditor transmits audit information whenever a userplaces a call. Several Regional Bell Operating Companies (RBOC's) haveinvested in systems that use collection prediction software, such as"PDAS", to provide data management of coin collections. The ability toaccurately monitor coin collections enables telephone companies tominimize or avoid the substantial economic losses experienced as aresult of skimming and the like.

There are many types of telephone auditors, but all of them suffer fromone or more of several drawbacks. For example, some prior art auditorsrequire extra communication lines to carry the information, while othersrequire additional power connections. In addition, many prior artstand-alone auditors require substantial modifications to existing cointelephones to enable the audit information to be recorded when a usermakes a call. Further, the prior art auditors transmit information whilethe handset is on-hook, and when a user picks up the handset, there isno dial tone and thus the user is prevented from making a call.

Furthermore, while smart payphones including audit functions provideadvantages not provided by older, dumb payphones, their adoption and usepresents many problems. For example, many smart payphone units are notas strong, durable and trouble-free as the dumb payphone units they aredesigned to replace. In addition, the electronic chassis used in thesmart payphone is many times more costly to manufacture, install andmaintain than a dumb chassis. Further, special skills are required toinstall, maintain and service smart payphones that are not comparable tothe skills required and currently exercised by service personnel whomaintain dumb payphone units. Yet further, some smart payphone units aremore complicated to use, sometimes causing customer dissatisfaction,whereas the dumb sets, as a result of their long usage, are familiar anduser-friendly. Most importantly, the RBOC's have a substantial capitalinvestment in standard or dumb payphones in use today, and thereforewish to extend their potential life expectancy for a number of years.Many of the RBOC's cannot justify abandoning their standard, dumbpayphones to adopt and use more costly, yet to be paid for, smarttelephones.

Thus, the incorporation of a simple and inexpensive coin auditor into adumb-chassis of a payphone is highly desirable. It also is desirable toprovide a simple, inexpensive electronic coin acceptor with auditcapability for connection to a dumb set, or to a smart set that may lackaudit capability.

SUMMARY OF THE INVENTION

We present a low-cost, electronic, line-powered and low-power integratedcoin acceptor that provides audit functions. In general, the integratedcoin acceptor contains coin validation and audit circuitry forvalidating deposited coins, and for monitoring, storing and transmittingaudit data. The integrated coin acceptor may be retrofit to a dumbpayphone chassis, or may be connected to a smart payphone chassis, onlyrequiring connection to the coin telephone. Further, the integrated coinacceptor requires no modification of central-office equipment, and canbe operated by telephone-network power alone.

In one aspect the invention is an integrated coin acceptor having a coinpassageway, at least one coin sensor, audit circuitry, telephone chassisinterface circuitry and control means. The control means, which mayinclude a microprocessor and associated circuits, is connected to thecoin sensor, audit circuitry, and to the interface circuitry. Theintegrated coin acceptor validates coins, refunds coins, monitors auditevents, saves audit data, and transmits audit data to a central office.

A preferred embodiment of the integrated coin acceptor may include thefollowing features. A battery connected to the control means, to thememory means and to the audit circuitry provides power in the event ofpower loss or when the payphone is on-hook. The audit circuitry includesa DTMF transceiver, RAM memory, EEPROM memory, real time clock, batterycontrol circuit, and a telephone line interface circuit. An indicatormeans is provided for indicating that adequate power exists on thetelephone lines to power the functions of the integrated coin acceptor.An event monitoring switch for installation in the housing of thepayphone reports when the vault door is opened or the cashbox removed.The event monitoring switch may comprise a bracket, a collar housing, amounting means, a plunger switch and a monitor line connected to theaudit circuitry. In addition, detection means monitors the telephoneline when the handset is on-hook, detects collect or refund operationsof the central office, and stores an indication of such occurrencewithout consuming telephone line power. The detection means may comprisea detection circuit, a collect latch, a refund latch, a control circuitand a battery. Furthermore, an off-hook detection circuit monitors thehandset during audit data transmission and generates an open switchinterval when the payphone goes off-hook. The off-hook detection circuitoperates so that a dial tone will be returned to the user in such asituation. The off-hook detection circuit may also be incorporated intoan audit device, and comprises a mechanical relay, an audit relay, acomparator and a control means.

Another aspect of the invention concerns a payphone event monitoringswitch for monitoring coin collections. The switch is installed usingpre-existing payphone chassis holes, and comprises a bracket, a collarhousing, a mounting means, a plunger switch assembly and a monitor line.The event monitoring switch is inexpensive, easy to install, and easy toconnect to the audit circuitry.

In another aspect of the invention, a loop length indicator circuit isdescribed for indicating if enough telephone line power is available toenable proper functioning of a coin operated telephone. The indicatorcircuit may comprise a monitor means, control means and an indicatormeans. The monitor means may be a voltage detect circuit, and theindicator means may comprise an LED, an audible tone driver, an audiblealarm or a combination of such indicators.

In yet another aspect of the invention, a circuit is provided for apayphone for detecting and storing central office collect and refundevents when the handset is on-hook. The circuit uses no telephone linepower and comprises a detection circuit, a collect latch and a refundlatch connected together in a bistable configuration, a control circuitand a battery.

Another aspect of the invention provides a low-power coin acceptor forattachment to a payphone chassis which includes an indicator means forindicating whether or not adequate telephone line power is available topower the payphone. The coin acceptor comprises a coin passageway, atleast one coin sensor, control means, monitor means and indicator means.The indicator means may comprise an LED, an audible tone driver, anaudible alarm or a combination thereof. The low power coin acceptor mayalso include audit circuitry.

The invention combines the proven reliability of an electronic coinacceptor with desirable coin accounting, telephone line powerindication, and off-hook detection functions. The detection circuitryreturns the dial tone to a user when she removes the handset from thehook-switch to go off-hook during audit communications. The detectioncircuitry also removes power from the payphone keypad to preventcorruption of the audit data. These features help to reduce costs forthe payphone owner by accurately accounting for deposited coins, byenabling the optimization of collection schedules, and by ensuring thata user may place a call whenever the payphone handset is taken off-hook.In addition, wiring complexity is reduced by the integrated coinacceptor because there are no direct connections to the telephonechassis hook-switch, which reduces installation time.

Other advantages and features will become apparent from the followingdetailed description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a coin-operated telephone connected to a centraloffice;

FIG. 2 is a partial cutaway side view of the upper portion of anembodiment of an integrated coin acceptor;

FIG. 3A is a perspective view of the embodiment of an integratedelectronic coin acceptor of FIG. 2;

FIG. 3B is a partial, cutaway perspective view of the upper housing of atelephone chassis to illustrate two possible mounting positions for asecurity switch;

FIG. 4 is a simplified schematic block diagram of an embodiment of acontrol board;

FIG. 5 is a simplified schematic block diagram of a coin recognitionboard;

FIGS. 6A, 6B and 6C are schematic block diagrams of telephone powerdetection circuits;

FIG. 7 is a schematic block diagram of a collect or refund detectioncircuit; and

FIG. 8 is a schematic block diagram of an off-hook detection circuit.

DETAILED DESCRIPTION

FIG. 1 shows a typical coin operated telephone or payphone 2 which isconnected to a central office 4 by three wires, the phone lines, whichare referred to as the tip 6, ring 8 and ground 9 lines. As shown inFIG. 1, phone 2 includes a handset 10 having a mouthpiece 11 and anearpiece 12 which are connected by a handle 13, a keypad 14, a coin slot16, and a coin return slot 18. When not in use by a customer, thehandset 10 sits in a cradle 19 depressing a spring-loaded hook switch20. When the handset 10 is in the position shown in FIG. 1, switch 20 isin its "on-hook" position. When handset 10 is lifted out of cradle 19,switch 20 is no longer depressed and it is then in its "off-hook"position.

The central office 4 applies various D.C. voltage amplitudes andpolarities on the tip 6 and ring 8, from which the phone 2 generates itsoperational power when the handset 10 is off-hook. The varying DCvoltages and an AC ringing voltage are interpreted by the coin telephone2 as providing operational commands for controlling its operation. Whenhandset 10 is on-hook, the phone 2 draws essentially no power from thetip 6 or ring 8 lines. The phone 2 typically does, however, performstatus monitoring in its standby state using a small amount of powerfrom an internal battery.

A customer picks up handset 10 to place a call thereby releasing theswitch 20 from its depressed position. The phone 2 enters its off-hookstate, and begins to draw power from the tip 6 and ring 8 lines toprocess the call. Next, the customer inserts a sufficient number ofcoins into the coin slot 16 to cover the cost of the call and dials thenumber using keypad 14. The dialed number is transmitted to the centraloffice 4 which connects the call. The customer completes the call byhanging up the phone, and then the money is collected by phone 2 when acollect signal from the central office 4 is received.

FIG. 2 is a partial cutaway side view of the upper portion of anembodiment of an integrated coin acceptor 30. A customer's coin 31 isshown being inserted through coin slot 16 in front panel 33 of the phone2. From the slot 16, the coin 31 travels past a plurality of coindetectors and sensors 34, 35, 36 and 37. After the last sensor 37, thecoin 31 falls onto a gate 38 which directs the coin 31 either to a coinescrow bucket 39 or to a return chute 40 which directs the coin 31 tothe coin return slot 18 (see FIG. 1) where it can be retrieved by thecustomer. In traveling from slot 16 to the coin escrow bucket 39 or thecoin return chute 40, the coin 31 travels along either an accept path Ashown as a solid line in FIG. 2, or along the reject path B shown as adashed line in FIG. 2.

Each of the sensors 34, 35, 36 and 37 produces an electrical outputsignal which serves as an input to a processing element ormicrocontroller or microprocessor which determines whether the coin isacceptable and its denomination. The microprocessor also produces outputsignals for controlling the position of the gate 38 so that the gate 38either directs the coin along path A or path B. The microprocessor alsocontrols a power supply for energizing the gate 38. Thus, themicroprocessor processes the electrical output signals from the sensors34, 35, 36 and 37, generates gate control signals, and controls the gatepower supply. The details concerning microprocessor control of the coindiscrimination and validation functions and gate functions are beyondthe scope of the present application, but can be found, for example, inU.S. Pat. Nos. 4,842,120 ("Jam Reducing Apparatus For Use In A CoinOperated Machine"), 4,953,681 ("Compact, Low Power Gate Apparatus ForCoin Operated Machines"), 4,538,719 ("Electronic Coin Acceptor"),5,167,313 ("Apparatus for Improved Coin, Bill and Other CurrencyAcceptance and Slug or Counterfeit Rejection"), 5,330,041 ("Apparatusfor Improved Coin, Bill and Other Currency Acceptance and Slug orCounterfeit Rejection"), and 5,443,144 ("Apparatus for Improved Coin,Bill and Other Currency Acceptance and Slug or Counterfeit Rejection"),which are assigned to the assignee of the present invention.Furthermore, additional details of low power control apparatus for apayphone are described in U.S. Pat. Nos. 4,926,458 ("Low Power ControlApparatus For A Coin Operated Telephone"), and 4,979,208 ("Method AndApparatus For Electronic Payphone Open Switch Interval Management"),both assigned to the assignee of the present invention. The disclosuresof these U.S. Patents are incorporated by reference herein.

FIG. 3A is a perspective view of the embodiment of an integrated,stand-alone electronic coin acceptor 30 of FIG. 2. The integrated coinacceptor 30 performs coin validation and audit operations, includingtransmitting audit data to a central office. The device 30 may beinstalled as original equipment in a payphone, or may be used as aretrofit to an existing dumb payphone chassis, for example, theWestern-Electric D-set chassis. Alternately, the integrated coinacceptor may interface with a smart chassis.

Referring to FIG. 3A, the integrated coin acceptor 30 contains a coinslot 16 leading to a coin passageway that contains the coin sensors (seeFIG. 2). A test button 42 and two LED's 44, 46 are present on the sideof the unit, which are used to initialize the audit function. (The LED'smay also be used to provide telephone status information, which isexplained below.) A battery cover 25 protects access to a replaceablebattery (not shown). The battery is a high-density, long-life batterypreferably having at least a 5-year life, and may be size "AA" and ratedat 3.6 volts and is used to power certain functions which will beexplained below. Connectors 47 accept the tip 6, ring 8 and ground 9lines. A security switch 49 comprising a collar housing 50 and a plunger51 is designed to monitor the vault door or the coin box within thepayphone chassis, and has a line 52 for connection to a receptacle 53 ofthe integrated coin acceptor. The security switch 49 is powered from thetelephone line or from the replaceable battery. A pig-tail male plug 55is shown for connection to female connector 56, and is used forconnecting the tip, ring and ground lines from the integrated coinacceptor to the telephone chassis. In addition, a 14-pin cable 57connected to the integrated coin acceptor plugs into the telephonechassis. The cable 57 supplies power and control signals between thetelephone chassis and the integrated coin acceptor, and may be modifiedto interface with the circuitry of various dumb or smart chassis.

When the integrated coin acceptor 30 is retrofit into an existingpayphone with a dumb chassis, the tip 6, ring 8 and ground 9 lines areconnected directly to the connector 47 and an installer uses test button42 to initialize and test the audit functions. For example, theinstaller lifts the handset 10 off-hook and dials a preset number forthe central office. A set-up protocol routine is then launched for theaudit circuitry of the integrated coin acceptor. When the set-up routineis finished, the installer depresses the test button and hangs-up thehandset. The audit function then executes, and at least one of the LED's44, 46 will illuminate to indicate that the audit operation is takingplace. When audit initialization ends, one or both LED's will illuminatefor a preset time and then extinguish to indicate to the installer thatthe audit routine was successful.

FIG. 3B is a partial, cutaway perspective view of the lower housing of atelephone chassis 45 to illustrate two of the possible mountingpositions, "A" and "B", for the security switch 49 of FIG. 3A. Amounting screw or other connection means 41 passes through a mountingcutout 48 of the collar housing to attach it to a bracket 43. The racket43 is capable of attachment to at least two pre-existing cutouts in thepayphone chassis. In position "A", the plunger 51 fits through anexisting square hole 54 in the front of the lower housing of thetelephone chassis 45 to monitor the vault door 58 of the payphone. Ifthe telephone chassis has been damaged due to vandalism such that thesquare hole 54 is deformed, the bracket 43 can be mounted in position"B" so that the plunger 51 will align with an existing round hole 59toward the rear of the chassis as shown. In this configuration, thesecurity switch 49 monitors the coin box (not shown) within thepayphone. The security switch 49 is easy to install, and does notrequire any drilling of holes into the lower housing of the telephonechassis 45. If the vault door is opened or the coin box removed, theswitch 49 sends a signal to the audit circuitry of the integrated coinacceptor 30. Thus, the security switch 49 monitors a physical event,namely the removal of the cashbox.

FIG. 4 is a simplified schematic block diagram of an embodiment of acontrol board 60 containing the electronic circuitry of the integratedcoin acceptor 30 of FIG. 3. The tip 6, ring 8 and ground lines 9 attachto the connector 47 and connect to the power control and relay drivers62, power supply 64 and driver 65. The power control and relay drivers62 are also connected to the connector 56, which is used to count theground, tip and ring lines to the telephone chassis. A microprocessor66, programmable logic device (PLD) circuitry 68, real time clock 70,and DTMF circuit 72 are connected together via standard data bus linesas shown. The DTMF circuit 72 is a transceiver, capable of bothtransmitting and receiving DTMF tone signals. Also contained on theboard 60 are line balance and coin credit circuitry 74, an off-hookdetect circuit 76, a reset circuit 78, power down and wake-up circuitry80, a gate driver 82, a battery power control circuit 84 connected to aconnector 54, a power switching circuit 86, a refund and collectdetection circuit 88, collect/refund/install switch latch circuitry 90,and an interrupt generator 92. In addition, the coin box switchconnector 53, battery connection 54, built-in self-test connection 94,harness connector 95 and a coin recognition board connector 96 (see FIG.5) are shown.

A suitable microprocessor 66 for use in the integrated coin acceptor 30is an 8-bit 80L31 microcontroller, which utilizes 3 volts to operate,contains 256 bytes of internal RAM, 16 K of ROM or EPROM and has amaximum clock speed of 20 MHz. The microprocessor 66 performs thefollowing tasks: coin validation, coin acceptance, chassis interfacefunctions, coin audit, built-in self-test (BIST) interface functions,communications software interface functions with the central office, andpower management functions. Audit events that are monitored and recordedinclude, but are not limited to, activation of the vault door switch orcash box removed, collect/refund occurrences, installation switchactivation, occurrences of certain DTMF tones on tip and ring lines,credit for validated coins, and real time clock alarms. Examples of whenthe microprocessor initiates an audit call to the central officeinclude, but are not limited to, when there is a coin box removed alarm,a collection event, a scheduled report, or when a test call is required.

The integrated coin acceptor 30 monitors all events that occur during anopen-switch interval (OSI), which are line power interruptions that maylast for 3 or more seconds, and maintains all critical information inbattery-powered memory. OSI's occur from time to time in response tocertain events such as user interaction, or an initial rate check,collect and refund occurrences and other events. In particular, the PLDcircuitry 68 includes random-access memory (RAM) which is separate orexternal to the microprocessor 66, and is backed-up with battery power.The external RAM contains the audit data and coin acceptance parametersand is always powered so that, in the event of loss of telephone linepower, all critical data including audit data will be preserved. Sincethe critical information already resides in external RAM, when an OSI isdetected there is no need to move data into memory. In contrast, priorart auditors attempt to save critical audit data as power is beingremoved, thus risking audit information corruption or loss.

The microprocessor 66 also is capable of entering a "power down" mode ofoperation when no instruction is being executed which eliminates busactivity. If an OSI occurs during this time, it is transparent to theintegrated coin acceptor 30, and nothing need be done. However, if themicroprocessor is executing instructions and an OSI occurs, then stepsare taken to enter a sleep mode of operation. In particular, themicroprocessor has a power fail input that is monitored periodically toassure that ample power is available to enable proper program execution.An active power fail input indicates power has been removed and that amaximum of 17 msecs of power is left. At such time, the microprocessorsuspends all activity and enters a sleep mode, to reduce the powerrequirements of the system and end bus activity. An internal timer ofthe microprocessor is used to interrupt the sleep mode at 1 msecintervals to check the power fail input. This sampling of the power failinput continues until power is depleted from the control board capacitoror the return of power is detected. Upon detection that normal power hasreturned, the microprocessor continues processing at the point it leftoff.

The power switching circuit 86 generates all of the voltages required torun the various functions of the control board. The tip 6, ring 8 andground 9 connections are switched through to the telephone chassis bythe power control circuit 62 depending on the logical condition of thecoin acceptor 30. Power from the chassis during normal coin chute mode,which is when a user lifts the handset off-hook so that power is derivedfrom the tip and ring lines, is input at connector 95 where the harnesscable 57 (see FIG. 3) connects.

The integrated coin acceptor 30 may contain a built-in self-test (BIST)function. The data interface lines are attached to connector 94 of theintegrated coin acceptor and to a personal computer. Service personneluse the personal computer and BIST function to test the integrated coinacceptor before shipment to a customer.

FIG. 5 is a simplified schematic block diagram of a coin recognitionboard 100. A connector 101 is used to interface the coin recognitionboard 100 to the control board 60 at connector 96 (see FIG. 4). Theboard 100 includes an application specific integrated circuit (ASIC)102, EEPROM circuit 104, LED's 44, 46 which may be green and red, testbutton 42, oscillator components 106, an oscillator enable circuit 108and a wake-up oscillator circuit 110. The ASIC 102 receives input fromthe oscillator components 106 which are connected to the sensors in thecoin passageway, and generates coin characteristic data that areutilized by the microprocessor 66 on the control board 60 to validatecoins.

When a payphone user picks up the handset, the microprocessor 66 entersthe coin chute mode of operation. During coin chute mode, credit signalsare issued on the nickel, dime, and quarter interface lines depending onthe coin accepted. In addition, the microprocessor controls the relayutilized for connecting the tip and ring lines to the telephone chassis,and switches the line balance circuitry during coin validation and tonegeneration. Tone generation is typically handled by the chassis. Thecoin credit data is monitored and stored in external random accessmemory (RAM), which is backed-up by the battery, so that it can betransmitted at a later time to the host computer at the central office.The audit data is transmitted in a format defined by the central office.

The audit mode of operation is defined as that time when the integratedcoin acceptor 30 has control of the tip 6 and ring 8 lines. When thehandset is on-hook and the integrated coin acceptor enters audit mode,power is derived from the tip and ring lines. In audit mode, themicroprocessor 66 establishes two-way communication with the centraloffice via the DTMF circuit 72. Such communication occurs at time ofinstallation, after an alarm from the real time clock 70 for a timedevent, or when a physical event occurs involving removing the coin boxor opening the vault door. The circuitry of the integrated coin acceptor30 associated with audit functions includes the DTMF circuit 72, thestatic RAM memory in the PLD circuit 68, EEPROM memory 104, real timeclock 70, battery and control circuitry 84, and the power control andrelay drivers 62 that interface to the tip and ring lines.

Power management for different operations are divided into severaldifferent modes by the integrated coin acceptor 30. For example, whenthe handset is on-hook and there is no activity then substantially nopower is consumed. During audit mode, the microcontroller 66, auditcircuitry and PLD circuit 68 are active and consume less than 20 mA.When the handset goes off-hook and the coin acceptor is waiting for coinarrival, the start-up oscillator 110 consumes less than 1 mA. When acoin is deposited and is being validated about 6 mA is consumed. Next,if the coin is accepted the accept gate 38 is moved and approximately 15mA is consumed, and during coin tone generation about 2.5 mA isconsumed. Thus, peak power is consumed when a user deposits coinscausing the accept gate 38 to operate and coin credit tones aregenerated on the tip and ring lines.

FIGS. 6A, 6B and 6C are simplified schematic block diagrams illustratingdifferent circuit configurations for detecting and indicating if enoughpower (at least 23 mA) is available from the central office to properlyoperate the coin operated telephone in the system. It should beunderstood that the circuits of FIGS. 6A, 6B and 6C could be part of theintegrated coin acceptor 30, or may be separately added to existing dumbor smart telephones. Each of the circuits measures power conditionswhich can be sampled at several locations, including the tip and ringlines, or Line Balance lines, the V_(external) line, or a combination ofLine Balance lines, the V_(external) line. Each circuit includes amicroprocessor with an associated power detect program or other logiccontrol circuitry, and means to indicate the power condition to servicepersonnel either visually or audibly. The microprocessor may be the samemicroprocessor 66 on the control board 60 of the integrated coinacceptor 30, or may be a separate unit.

FIG. 6A is a simplified schematic diagram of a loop length indicatorcircuit 120 that may be installed in a payphone. A voltage detectcircuit 122 is connected to an A-relay coil 132 and balance network 134contained in a payphone chassis 130. The payphone chassis 130 may housea dumb set or a smart set, and has the tip 6 and ring 8 lines connectedto it. The diode bridge 136, A-relay coil 132 and balance network 134generate signals on the Line Balance In line 138, Line Balance Out Line140 and V_(external) 142 line. The balance network 134 is generallyconsidered a voltage source and maintains a relatively constantimpedance between the tip and ring lines by shunting current to groundas required. The Line Balance In line 138 is the high side in terms ofvoltage of the balance network 134, and the Line Balance Out line 140 isthe low side in terms of voltage, with current flowing back out to thechassis 130 through the Line Balance Out line when needed. Line BalanceIn is connected to Line Balance Out via a switch and a 33 ohm resistor(not shown), except when the accept gate is energized and then the 250ohms of the gate resistance is substituted for the switch, in serieswith the 33 ohm resistor. The V_(external) line 142 is derived from theLine Balance In line and is best modeled as a zener diode voltage sourceconnected to ground on one end, and as a resistor to the Line BalanceOut line on the other end as shown.

The voltage level present on the Line Balance In line 138 isproportional to the loop current as the Balance Network 134automatically adjusts the load impedance for various loop lengths. Thevoltage on Line Balance In line 138 is interpreted by the Voltage DetectCircuitry 122 which signals the control logic circuit 124 if less thanthe minimum loop current is detected. The control circuit 124 thenactivates either a visual warning indicator such as an LED 126, or anaudible alarm circuit or both. The visual warning indicator may be oneor both of the LED's 44, 46 shown in FIG. 3A. Alternately, a tone or aninterference signal may be injected into the earpiece 11 of handset 10(see FIG. 1) via the Line Balance Out line 140.

Again referring to FIG. 6A, instead of monitoring the Line Balance Inline 138, the Voltage Detect circuitry 122 could monitor the voltage onthe V_(external) line 142. In particular, the voltage on theV_(external) line 142 is in regulation when sufficient loop current of23 mA or more exists. As loop current drops, V_(external) no longerstays in regulation, indicating a fault. The voltage on the V_(external)line 142 is then interpreted by the Voltage Detect Circuitry 122, whichsignals the control circuit 124 if less than minimum loop current isdetected. The control circuit then activates either a visual warningindicator or other indication means, as discussed above.

Alternately, the indicator circuit 120 of FIG. 6A may measure thecurrent flowing from the Line Balance In line 138 to the Line BalanceOut line 140, which is converted to a representative voltage by the 33ohm resistor. The voltage across the resistor is then interpreted by theVoltage Detect Circuitry 122, which signals the control circuit if lessthan minimum loop current is detected. A visual warning indicator suchas an LED, or other indication means, is then activated as discussedabove.

FIG. 6B is a simplified schematic diagram of a loop length indicatorcircuit 121 incorporating voltage detect circuitry 122, a controlcircuit 124, an LED indicator 126 and a sampling device 128. Thesampling device 128 is shown in series with the ring line 8 but may bein series with the tip line 6, and senses the current on the line. Theoutput of the sampling device is interpreted by the Voltage DetectCircuitry 122, which signals the control circuit if less than minimumloop current is detected. The control circuit then activates a visualwarning indicator such as the LED 126, or an audible alarm circuit orboth. Alternately, a tone or an interference signal may be injected intoearpiece 11 of the handset 10.

FIG. 6C is a simplified schematic diagram of a loop length indicatorcircuit 150 that would be connected directly to the tip 6 and ring 8lines of the telephone system. The voltage measured tip to ring when thetelephone is in the off-hook state is proportional to the loop currentflowing, and thus the voltage detect circuit 152 is designed to becapable of surviving high voltage transients. The voltage between thetip and ring lines is interpreted by the voltage detect circuit 152which signals the control circuit 154 if less than minimum loop currentis detected. The control circuit 154 then activates either a visualwarning indicator such as the LED 156, or activates an audible tonedriver circuit 158 to inject a tone or an interference signal into theearpiece 11 of the handset 10 via the Line Balance In line, or otherwiseprovides an indication for a serviceman.

FIG. 7 is a simplified schematic block diagram of a collect/refunddetection circuitry 88 that detects and stores collect and refundinformation while the telephone is on-hook, consuming substantially nopower from the telephone line. The circuit 88 may be part of theintegrated coin acceptor 30, or may be part of a separate auditorcircuit for attachment to either a smart or dumb telephone chassis.Referring to FIG. 7, the tip line 6 is connected to a detection circuit172 which is connected to a battery 174. The battery and the detectioncircuit are also connected to two latches, 176 and 178, which areconnected together in a bistable configuration, and the latches andbattery are connected to a control circuit 66 or microprocessor.

When a user hangs up the handset after a call, the telephone hook switch20 is open as shown in FIG. 7, and the central office performs either acollect or refund operation. The central office removes tip to ringpower and applies tip to ground power to cause the escrow bucket in thetelephone chassis 130 to operate. Typically, a tip to ground current of41 mA or greater for a period of 350 msecs or greater indicates coindisposal, wherein a positive polarity signal indicates coin collectionand a negative polarity signal indicates a refund. During this time,there is no tip to ring power but the audit information is important andmust be recorded. Thus, the detection circuitry 88 performs thedetection and information retention function as follows. When a collector positive signal of 41 mA lasting 350 msecs or more is detected by thebattery-powered detection circuit 172, it sends a signal to set latch176. Similarly, if a refund or negative signal of the same strength isdetected, then a signal is sent to set latch 178. Once one of thelatches is set the other latch is locked out until a reset signal online 179 from the control circuit 66 resets the latches. Thus, a collector refund event is captured without using any power from the tip andring lines, and by using minimal power from the battery 174.

When a user removes the handset to go off-hook, or if an audit eventoccurs, tip and ring power is restored and the circuitry of theintegrated coin-acceptor 30 wakes up. The state of the latches 176 and178 is then checked by the control circuit 66, and if latch 176 has beenset, then the coin count stored in memory is updated. The controlcircuit 66 next issues a reset signal on line 179 to reset both latchesin preparation for new information that may be generated after the userhangs up.

FIG. 8 is a simplified schematic block diagram depicting the off-hookdetection circuit 76 (also shown in FIG. 4) of the integrated coinacceptor 30. The detection circuit 76 may be telephone line or batterypowered. In addition, one skilled in the art understands that theoff-hook detection circuit 76 could be added to an existing telephoneauditor or other stand-alone circuitry.

The off-hook detection circuit of FIG. 8 functions to detect when thehandset 10 is removed from the cradle 19 (see FIG. 1) during the timethat the integrated coin acceptor is in audit mode. This is an importantevent because, when the telephone goes off-hook during audit mode, thedial tone must be provided to the user and steps must be taken toprevent corruption of the audit information that was being transmittedto the central office.

Referring to FIG. 8, tip 6, ring 8 and ground 9 lines from the centraloffice come directly into the integrated coin acceptor 30. The tip andring lines are connected to the telephone chassis 130 through amechanical relay 160 or similar control device. The ground line isconnected to the connector 47 and directly to the connector 56. Duringnormal operation of the payphone, the switches of the relay 160 areclosed, the switches 163 and 165 of the audit relay 162 are open, andthe switch 167 is closed. Thus, the ground line 131 between the chassisand the integrated coin acceptor is normally connected. When the handset10 is on-hook, the hook switch 20 is opened, as shown. When a userwishes to place a call, the handset is lifted from its cradle causingthe hook switch 20 to close, and the central office provides a dialtone.

When the integrated coin acceptor 30 enters audit mode with the handseton-hook, then the audit relay 162 is energized so that the switches 163and 165 close to connect the tip and ring lines through the bridgecircuit 164 to the microprocessor 66. The central office then supplies adial tone as the coin acceptor 30 powers up using the voltage suppliedthrough the audit relay 162. (The audit relay 162 is battery-powered andis part of the power control circuitry 62 shown in FIG. 4.) Themicroprocessor 66 recognizes an audit event and causes a pre-programmedtelephone number stored in battery backed-up memory to be dialed so thataudit information can be reported. Once dialing begins, the centraloffice removes the dial tone. Therefore, if a user now tries to place atelephone call by picking up the handset during audit communications,unless steps are taken to quickly terminate the audit mode and returndial tone, she may hear the audit transmission and will not be able tomake a call.

During an audit mode call-in-progress, the audit relay 162 is acting asthe hook switch and switches 163 and 165 are closed to provide power tothe integrated coin acceptor 30, but switch 167 is open to disconnectthe ground line 131 between the chassis and coin acceptor. When thehandset is taken off-hook, the hook switch 20 closes causing a voltageto be generated by bridge circuit 136. The A-relay coil 132 is thenenergized to send a signal v_(sense) to comparator 166 which generatesan off-hook signal 161 input to microprocessor 66. This off-hook signalis recognized by the microprocessor as a request for dial tone, and themicroprocessor generates an OSI sequence by utilizing the mechanicalrelay 160 and audit relay 162. In particular, upon encountering theoff-hook signal the microprocessor energizes the mechanical relay 160 toopen its switches to isolate the chassis 130 from the tip and ringlines. The audit call in progress is then rescheduled to a future timeand an OSI time interval of at least 3 seconds is programmed to the realtime clock 70 (shown in FIG. 4) to guarantee that a new dial tone willbe generated by the central office. The audit relay 162 is thenenergized to open its switches to isolate the integrated coin acceptor30 from the tip and ring lines, resulting in an open loop condition.When the OSI time interval of at least 3 seconds elapses, the auditrelay 162 is energized to connect the tip and ring lines, causing theintegrated coin acceptor 30 to power on with a new dial tone. As thisoccurs, the microprocessor 66 recognizes that the dial tone resultedfrom a self-initiated OSI, and causes the mechanical relay 160 to closeand the audit relay 162 to open. Consequently, the dial tone is returnedto the chassis handset to complete the OSI sequence and to permit a userto place a telephone call.

Consequently, when a user picks up the handset to close hook switch 20during audit mode, the off-hook detection circuit 76 senses a change inthe voltage between the chassis 130 and the integrated coin acceptor 30rather than directly monitoring the state of the hook switch 20. Themicroprocessor 66 then proceeds with an open switch interval (OSI)sequence, as explained above. The audit information is further protectedby proceeding in this manner because when an OSI occurs the tip 6 andring 9 lines are disconnected from the chassis which removes power anddisables the payphone keypad 14 (see FIG. 1). This prevents a telephoneuser from unintentionally corrupting the audit data by insertingadditional DTMF tones from the keypad into the audit information.

If an off-hook event is detected during audit mode but before theintegrated coin acceptor 30 dials the central office, the audit event isrescheduled using the real time clock 70 and the audit relay 162 isopened. Thus, the current dial tone that was going to be provided to themicroprocessor by the audit relay 162 for audit purposes is merelyre-routed through the mechanical relay 160 to the handset 10 to enable auser to place a telephone call.

An integrated coin acceptor for a payphone that contains audit circuitryand functions has been described. The integrated coin acceptor is fullycompatible with the audit software used by the central office, and isdesigned to assure a seamless transition between coin acceptor operationand audit data recording and transmission. Components related to theaudit function include a DTMF transceiver, static RAM memory, EEPROMmemory, real time clock, battery and control circuits for dataretention, and a interface circuitry to the tip, ring, and ground lines.Several other components and circuits, including a cashbox securityswitch for mounting into an existing hole in the telephone chassishousing, and a simple interface circuit to aid in initializing the auditfunctions and for checking the telephone line power availability havebeen disclosed. During audit interrogation activity, the integrated coinacceptor takes control of the phone line, but contains circuitry thatreturns the dial-tone to the user if an off-hook event occurs. Thus, thedescribed low-power, integrated coin acceptor is a low cost solution forproviding improved coin validation and audit functions for a dumbpayphone chassis or to a smart payphone chassis.

What is claimed is:
 1. A payphone event monitoring switch assembly forinstallation in a standard payphone housing using preexisting payphonechassis cutouts, to generate a signal for use by an audit circuit tomonitor the collection of coins, comprising:a bracket capable ofattachment to preexisting cutouts in the payphone in either a forward ora rear position; a collar housing having a mounting cutout forconnection to the bracket; a mounting means for attaching the collar tothe bracket; a plunger switch assembly connected to the collar housinghaving a plunger that fits through a first existing hole in the payphonechassis if the bracket is in the front position to monitor the vaultdoor, or fits through a second existing hole of the chassis if thebracket is in the rear position to monitor the coin box; and a monitorline connected to the plunger switch and for connection to the auditcircuitry for providing a signal indicating the collection of coins. 2.The apparatus of claim 1, further comprising:a battery connected to themonitor line for supplying power to the plunger switch.
 3. A securityswitch assembly for retrofitting to the lower housing of a payphonechassis to monitor either the payphone vault door or the cashbox,comprising:a bracket for installation in one of two positions in thelower housing; a collar housing having a mounting cutout for connectionto the bracket, the collar housing containing electronic circuitry; aplunger connected to the electronic circuitry of the collar housing; andan output line connected to the electronic circuitry, wherein a signalis generated when the plunger is moved to indicate either that the vaultdoor has been opened or that the cashbox has been removed depending onwhich position the bracket has been mounted.